Waterjet cutters have been in use for the last decade to cut a wide variety of materials. Such a cutter commonly utilizes a source of high pressure liquid such as a hydraulic intensifier, a conduit system and a nozzle. Such a system is described in U.S. Pat. No. 4,435,902. One element of such a device is a catcher to absorb the energy of the cutting after the work is done. A typical catcher is a tube filled with a liquid.
Entraining abrasive particles in ultra-high pressure (over 20,000 psi.) waterjets has vastly improved cutting performance. Though still in the development stages, the abrasive-waterjet cutting techinque has already displayed its advantages over conventional methods in several special applications. It is now possible to effectively cut many materials that could not be cut with waterjets alone, including metals, ceramics, glass, etc.
To develop the market potential of this technique, it is necessary to reduce or eliminate a few critical limitations which prevent it from being widely adopted by the industry. One of the most severe limitations is lack of equipment portability. Other limitations include the lack of an efficient system to catch water and spent abrasives, and the high noise level associated with the breakup of the abrasive-waterjet stream.
Abrasive particles are highly destructive, even after cutting through hard materials. Currently, the energy of the abrasive-waterjet is dissipated in a water tank at least 2 feet deep. Shallower vessels have proved ineffective, because a stationary abrasive-waterjet can easily cut through 0.25" steel plate at the bottom of a 15" water column. Thus, an X-Y table requires a tank large enough to cover the maximum cutting area. The bulky tank restricts maneuverability, which is a prerequisite for robotic and many factory applications. Further, the action of the abrasive-water jet churns the water and abrasives in the catcher/tank, increasing spillage. Also, frequent cleaning of the catcher/tank is necessary to remove used abrasives and residues that accumulate during cutting. Aside from these problems, the tank itself serves as a reesonator that radiates noise. It is extremely difficult to incorporate an effective noise suppression device into such a system.
The following criterion have been established to describe a catcher for waterjets and abrasive-laden waterjets:
1. Adequate protection to the wall and bottom of the catcher PA0 2. Minimal size and weight for portability and maneuverability PA0 3. Minimal vibration to facilitate accurate cutting performance PA0 4. Facilitate discharge of water and abrasives to a hopper for ease of removal and clean up PA0 5. An effective noise suppression device to protect operators
An attempt has been made to use a 24" long tube catcher filled with water alone. However, this length may be unacceptable for many factory applications, especially robotic operations, and the water column is inadequate unless a carbide plug is used to protect the bottom of the catcher. In cutting operations the deflection of the abrasive-waterjet causes severe damage to the tube wall. The longer the catcher, the more vulnerable is the side wall. A wear-resistant liner such as a carbide sleeve for the tube catcher inner wall would be quite expensive.